FIG. 1 depicts a conventional method 10 for fabricating a conventional perpendicular magnetic recording (PMR) pole of a conventional PMR transducer. FIGS. 2-4 depict the conventional PMR head 50 during fabrication using the conventional method 10 as viewed from the air-bearing surface (ABS). For clarity, the conventional PMR head 50 is not to scale. Referring to FIGS. 1-4, the method 10 commences after formation of an alumina underlayer. A conventional seed layer, such as Ru, is deposited, via step 12. A conventional bottom antireflective coating (BARC) layer of SiN is typically, deposited, via step 14. The conventional BARC layer may be used to reduce or eliminate reflections from the underlying substrate
A photoresist layer is provided on the conventional BARC is provided on the conventional BARC layer, via step 16. FIG. 2 depicts the conventional PMR head 50 after step 16 is provided. The conventional PMR head 50 is typically a merged head including a conventional PMR write transducer 60 and a read transducer 80. Thus, the conventional read head 80 typically includes a first shield 82, a read sensor 84, and a second shield 86. The read head 80 may be separated from the PMR write transducer 60 by an insulator 54. The conventional PMR transducer 60 includes a first pole 62 and alumina underlayer 64. The conventional seed layer 66 and conventional SiN BARC layer 68 have also been formed. Also shown is the photoresist layer 70.
The photoresist layer 70 is patterned, via step 18. Typically, step 18 is performed utilizing photolithography. Step 18 includes forming a trench in the photoresist layer 70 in which the conventional PMR pole is to be formed. FIG. 3 depicts the conventional PMR head 50 after step 18 has been completed. Thus, a trench 71 has been formed in the photoresist 70′. At the base of the trench 71, footings 73 exist. In addition, because a PMR pole is being formed, the trench 71 has a reverse angle. Stated differently, the angle, θ, is less than ninety degrees. The magnetic material for the PMR pole is deposited via step 20. Step 20 also may include removing an exposed portion of the conventional BARC layer 68 at the base of the trench. Thus, the trench 71 is at least partially filled. Fabrication of the conventional PMR head 50 is completed, via step 22. Step 22 may include removing the resist 70′, performing a pole trim and/or chemical mechanical polish (CMP), as well as forming other structures, such as shields. FIG. 4 depicts the conventional PMR head 50 after completion of the method 20. Consequently, the PMR pole 72 has been formed. During formation, a portion of the conventional BARC layer 68 is removed. Subsequently, the resist mask 70′ and exposed portions of the BARC layer 68 and seed layer 66 are removed. Thus, only a portion of the seed layer 66′ remains. Although shown separately, the seed layer 66′ might be indistinguishable from the PMR pole 72. In addition, an insulating layer 74 substantially surrounding the sides of the PMR pole 72 has been provided. In addition, a write gap 76, optional conventional top shield 78, and insulator 79 are also fabricated. The PMR transducer 60 may also include a second pole (not shown) and pole pads (not shown). The shape of the PMR pole 72 substantially conforms to the shape of the trench 71. Consequently, the conventional PMR pole 72 has reverse angle, θ. The conventional PMR head 50 may thus be formed.
Although the conventional method 10 and conventional PMR head 50 function, there are drawbacks. Although the conventional Ru seed layer 66 enables growth of the PMR pole 72, the conventional seed layer 66 is typically strongly reflective. As a result, placing the resist layer 70 directly on the conventional seed layer 66 would adversely affect photolithography used in patterning the photoresist layer 70 in step 18. Use of the conventional SiN BARC layer 72 substantially reduces the reflection from layers below the photoresist layer 70. Consequently, unwanted optical effects due to reflections from the conventional seed layer 66 may be reduced or eliminated.
Although the conventional BARC layer 68 improves the photolithography, use of the conventional BARC layer 68 results in footings 73 that adversely impact the conventional PMR head. The footings 73 are generally believed to be caused by an acid-base interaction between the acidic resist 70 and the basic conventional BARC 68. This interaction is known as resist poisoning. The footings 73 limit the trench line width resolution and increase scumming. As a result, the conventional PMR pole 72 formed within the trench 71 has an increased width. In addition, the process window is decreased. The line width thus varies sharply with a change in the focus conditions for photolithography. In addition, there is a greater variation in the critical dimension of the trench 71 between devices 50. Consequently, processing may need to be more tightly controlled. Thus, performance and manufacturability of the conventional PMR head 50 may be adversely impacted.
Methods have been proposed for removing the footings 73. Such techniques include utilizing an acid treatment and an oxygen plasma treatment of the surface of the conventional BARC layer 68. The acid and oxygen plasma treatments are reported to reduce the footing 73 and reduce scumming. However, such methods may be of limited utility. Particularly in the context of head formation, such treatments may not adequately remove the footings 73.
Accordingly, what is needed is a system and method for improving the fabrication of a PMR head.